Stereophonic tonal output from single audio input channel



Nov. 10, 1964 J. MARKOWITZ 3,

STEREOPHONIC TONAL OUTPUT FROM SINGLE AUDIO INPUT CHANNEL Filed May 10, 1960 2 Sheets-Sheet 1 Fig.

l I a l' l I I SIGNAL SOURCE United States Patent 3 156,769 STEREGPHONIC TONAL OUTPUT FROM SINGLE AUDH) INPUT CHANNEL Jerome Marlrowitz, 821 N. 30th St., Allentown, Pa. Filed May 10, 1960, Ser. No. 28,145 2 Claims. (Cl. 179-1) This invention relates to electrical musical instruments such as electrical organs, electric phonographs, radios, etc., embodying an electrical system which produces, or reproduces, sounds, tones, or music, and also concerns an amplifier-loudspeaker arrangement for such a system, capable of imparting to the normal sounds emanating therefrom a certain stereophonic quality, or eiiect similar to that produced by a group or relatively spaced sound sources such as the pipes of a pipe organ or the different instruments of an orchestra.

Electrical musical instruments such as modern electrical organs, or reproducers such as modern electrical record and tape players are provided with an amplifier and loudspeaker unit arrangement from which the electrically produced tones are emitted. When a stereophonic effect is desired in an electrical organ, the practice is to feed the output of a tone generator to an amplifier loudspeaker combination and the output of a second tone generator or output circuit to a second amplifier and loudspeaker which is relatively spaced from the first one. In an electrical phonograph system a similar arrangement is employed except that one pre-recorded channel is fed through one amplifier and speaker and another channel feeds a second amplifier and speaker.

I am aware of attempts to provide a stereophonic effect from a given single channel or audio current by feeding the signal into two or more separate amplifier and spaced speaker units and to provide for cyclicly switching from one speaker to another or cyclicly varying the output of one or both speakers. Such arrangements do provide a stereophonic quality which may have value in connection with a tremolo, vibrato 0r celeste effect, however, such systems are useless when used with recorded music or sound because of the additional beat which is imparted to the signal. These systems are also of little value to an electrical musical instrument when a straight effect is desired. In every case a discriminating listener will rebel at the monotony of the cyclical variation in tone.

The problem of overriding the indicated deficiency existing in the aforementioned system when it is desired to provide a stereophonic effect from a single audio signal has heretofore, to my knowledge, not been solved.

One object of my invention is to provide special circuitry and an amplifier-speaker system which will provide stereophonic effects from a single input signal of generated or recorded sound without the defects of previous systems.

An additional object of my invention is to provide an amplifier loudspeaker system which will add random pitch and intensity variations to signals which are passed through it.

Another obiect of the invention is to provide stereophonic effects from a single audio signal including means for providing that these effects will be complete random in character so that they cannot easily be analyzed, even by a trained listener.

In the accompanying drawing:

FIGURE 1 is a drawing which illustrates the operation of the invention incorporated in a dual amplifier system.

FIGURE 2 is an illustration which shows means which are necessary for incorporating the invention in a three or more amplifier system.

For purposes of exemplification, or illustration, my invention is herein disclosed as embodied in, or applied to a standard, or conventional type electronic organ or record player. However, it is to be noted that only those parts have been shown in the drawings as are deemed necessary to facilitate a clear understanding of the construction and operation of my invention, the performance of its intended purpose and the manner in which it achieves certain unique and desirable results and advantages. From this disclosure it will be readily apparent to those skilled in this art how my invention can be utilized in the same or similar manner with electronic organs, electronic phonographs or the like in general.

Since the desirability of stereophonic effects and tone dispersion have been widely discussed in various printed media during the past few years, it is not considered necessary in this application to cover them. The various aspects of these phenomena are generally well understood by those versed in the art.

In FIGURE 1, certain of the well-known parts of a stereophonic audio system are indicated. These parts comprise an amplifier 1 and associated speaker S, an amplifier 2 and associated speaker S and a signal source 3. Were this signal source to be of a dual channel nature, these elements would constitute the usual equipment of a standard stereophonic audio system and as such form no part of my invention when utilized in the manner of the prior art practice.

My invention comprises the arrangement of novel means in operational combination and co-operating relationship with said elements, devices and parts, as about to be described.

In the form of my invention, shown in FIGURE 1, the said novel means comprises, in addition, a noise generator 4 which represents a random voltage source. Such a device is manufactured by the Grason-Stadler Company of West Concord, Massachusetts and is their Model 901A. This random voltage source is connected so as to trigger an electronic switch 5 which in turn is connected to a pair of lamps carrying designations l4 and 2d.

Specifically noise generator or random voltage source 4 is connected by means of lines 6 and '7, to a low pass filter which consists of inductor t5 and capacitor 9. The purpose of this filter is to eliminate many of the upper frequency components of the noise generator which are not required for this particular function. Output from the low pass filter passes through coupling capacitor 10 into the bistable type transistor electronic switch 5 which consists of transistors 11, 16 resistors 12, 18 and capacitors l3, l9 and resistor 29. Output from this electronic switch feeds lamp 14. The other terminal of lamp 14 is connected to a battery or power source 15. Lamp 14 will glow only when electronic switch transistor 11 conducts due to an input pulse of the proper polarity. The output of transistor 11 is also coupled to a second electronic switch consisting of transistor in, resistor 18 and capacitor 19, through line 17. Output of transistor 16 is connected to one terminal of lamp 243 while the opposite terminal of this lamp is also connected to the power source 15. Lamp 2t) will only glow when transistor 16 conducts. This will necessarily occur only when transistor 11 is not conducting. Consequently, the lamps 14 and 29 will glow in an out of phase relationship.

Lamps 14 and 2% are located in an enclosure, in close proximity to light dependant resistors 21 and 22 respectively. The resistance of these units varies inversely with the amount of light to which they are exposed. It will be observed, therefore, that when light dependant resistor 21 has maximum resistance, light dependant resistor 22 will be at minimum resistance. Generally speaking, the function of the lamps is to provide a medium which will respond only to relatively low frequencies and in a smooth, linear fashion, otherwise sharp pulses could be transmitted into amplifiers 1 and 2 with consequently undesirable tonal effects.

Signal source 3 feeds amplifiers 1 and 2 through isolating resistors 23 and 24. Light dependant resistors 21 and 22 are effectively shunted across the inputs of amplifiers l and 2 and will vary the signal inputs depending upon the lamp fiutuations, the setting of adjustable resistors 25 and 26 and the size of capacitors 27 and 28. Adjustable resistors 25 and 26 represent the means for balancing the relative activity of the signal input to each amplifier. 7

If the speakers are relatively and properly spaced, the effect upon the listener will be that of a wide front of sound not unlike that of ordinary dual channel stereo.

Since only a single audio channel is required, it follows that if this system is applied to a simple electrical organ with a single output channel, a much more satisfying tone will result. In addition to the pleasing stereo quality achieved, the listener will also hear the random pitch and intensity variations which are so characteristic of pipe organs.

The system may also be connected to a single channel radio, tape or disc player with similar advantages. It should be noted that orchestral recordings, for instance, generally have a much higher order of activity and harmonic content as compared to the output of a simple electrical organ. When reproducing music of this type, the random pitch and intensity variations do not in way detract from the end result because of the additional pitch fringe content which is inherent in such music.

1 In this description no attempt has been made to describe the various tonal controls, bass and treble boosts, etc., which are the deli ht of the average audiophile since their application is well known.

In FIGURE 2 certain of the parts of a 3 channel stereo system are shown. These parts comprises amplifiers 1a, lb and 1c and associated loudspeakers S, 81 and S2, and signal suorce 3a.

Signal source 3a feeds its voltage output through lines Y and isolating resistors ll, 11a and lllb to amplifiers la, lb and lie.

Numeral a indicates a combined electronic switch, lamp and photo sensitive resistor device. The electronic switch is similar to that indicated in FIGURE 1 except that only a single lamp is controlled by the bistable transistor switch. The random voltage output of noise generator 4a is channeled into inductor 8a and capacitor 9a, representing the low pass filter. Filtered random voltage passes through coupling capacitor a and controls the associated electronic switch, lamp, photo sensitive resistor, and amplifier in the manner previously described. Numeral 5a may be referred to as a frequency selective electronic switch-photo sensitive resistor combination.

However, in addition to unit 5a frequency selective electronic switch-photo sensitive resistor combinations 5b and 5c are employed to produce random variations in the output of amplifiers 1b and 1c respectively. If low pass filters 8b, 9b and 8c, 9c are turned to somewhat different frequencies than that of filters 3a, 9a it will be apparent that the photo sensitive resistors with which they are associated will fluctuate in resistance at differing and out of phase rates. This is because each filter will select its own frequency band from the large selection of varying frequency components which-are ever present in a noise signal.

The tonal result achieved by the arrangement shown in PiGURE 2 will be a triple stereo effect since the signals of each of the three speakers will constantly vary at a random and ever-changing out of phase rate. As many additional frequency selective switches and controlled amplifiers as desired may be'employed to produce a broad tonal front. Many unusual effects can be produced by changing the relative positions of the louderspeakers and their associated activity controls.

Of course, it will be apparent to those skilled in this art that the novel amplifier-louderspeaker system developments specifically shown and described, can be changed and modified in various ways, without departing from the invention herein disclosed and more particularly defined by the hereto appended claims.

For example, while I have shown the light dependant resistors connected in shunt with the input to their associated amplifiers, they could be connected at their points in these amplifiers. If an arrangement similar to that shown in FIGURE 1 is applied to each channel of a standard stereo system, an eifect similar to four channel stereo would be produced.

The advantages of this invention would be of great value to radio and television broadcasting where stereo effects could be obtained without in any way changing the existing frequency allocations or transmitting equip ment. If the output signal of random voltage source 4 is sufficient, it would be feasible to dispense with the electronic switch. With such an arrangement the filtered random voltage signal could be applied directly to lamps 14 and Ztl of FIGURE 1 through a centertapped transformer which would supply the opposite phase voltage to these lamps. It would also be possible, with certain amplifiers, to apply the filtered random voltage directly to a bias point thereby controlling the output signal.

I claim:

1. An amplifier loudspeaker unit for an electrical sound producing system comprising a signal source, a connection from said signal source to a first amplifier and louderspeaker, a connection from said signal source to a second amplifier and loudspeaker, a random voltage source, an electronic switch with dual output points in opposite phase triggered from said random voltage source, a lamp connected to each output point of said electronic switch, a photo sensitive resistor in proximity to each lamp and a connection from each photo sensitive resistor to each amplifier so that the signal from the random voltage source will cause the output of the first amplifier and louderspeaker to vary in opposite phase to that of the second amplifier and loudspeaker.

2. An amplifier loudspeaker unit for an electrical sound producing system comprising a plurality of amplifier and associated loudspeakers, a signal source, a connection from saidsignal source to said amplifiers, a random voltage supply, means for causing the random voltage supply to vary the output of all amplifiers, said means including a frequency selective electronic switch for each amplifier, a lamp for each switch whose intensity is varied by the action of said switch and a photo sensitive resistor in close proximity to each lamp and a connection from each photo sensitive resistor to each amplifier arranged to control the output signal of the amplifier loudspeaker unit with which it is associated.

References Cited in the file of this patent UNITED STATES PATENTS 7 2,273,866 Holst et al. Feb. 24, 1942 2,418,119 Hansen Apr. 1, 1947 2,481,576 De Boer Sept. 13, 1949 2,517,783 Glass et al. Aug. 8, 1950 2,701,305 Hopper Feb. 1, 1955 2,792,449 Bottini May 14, 1957 2,876,395 Miller Mar. 13, 1959 2,927,963 Jordan et al. Mar. 8, 1960 

1. AN AMPLIFER LOUDSPEAKER UNIT FOR AN ELECTRICAL SOUND PRODUCING SYSTEM COMPRISING A SIGNAL SOURCE, A CONNECTION FROM SAID SIGNAL SOURCE TO A FIRST AMPLIFIER AND LOUDERSPEAKER, A CONNECTION FROM SAID SIGNAL SOURCE TO A SECOND AMPLIFIER AND LOUDSPEAKER, A RANDOM VOLTAGE SOURCE, AN ELECTRONIC SWITCH WITH DUAL OUTPUT POINTS IN OPPOSITE PHASE TRIGGERED FROM SAID RANDOM VOLTAGE SOURCE, A LAMP CONNECTED TO EACH OUTPUT POINT OF SAID ELECTRONIC SWITCH, A PHOTO SENSITIVE RESISTOR IN PROXIMITY TO EACH LAMP AND 